Improvement of Intracranial Time of Flight MR-Angiography with a Subtraction Method

Abstract

Italian

Our purpose was to evaluate a novel 3D Time-of-Flight (TOF) MR-Angiography (MRA) method, aimed at improving contrast resolution between vessels and static tissues.

The new method consists of the acquisition of two MRA sequences, the first with the conventional technique and the second with arterial saturation. After the acquisition, digital subtraction between the two sequences was carried out to obtain a set of partitions with high flow signal and very low parenchymal signal. Five healthy volunteers and 16 patients with vascular brain diseases were studied. The resulting images were then reconstructed with maximal intensity projection (MIP) and compared with TOF MRA.

In healthy volunteers subtraction-TOF showed higher contrast resolution and better visualization of small arterial vessels than the TOF technique. In the group of patients, visualization of turbulent flow lesions (i.e. aneurysms) was the same with both methods. In contrast, subtraction-TOF was superior to TOF for small vessel visualization (i.e. treated arteriovenous malformations) and for complete suppression of elevated signal intensity areas due to hematic debris (metahemoglobin).

In conclusion, subtraction-TOF is a useful technique if small brain vessel visualization is required or to suppress short T1 static tissues (i.e. metahemoglobin).

Keywords

magnetic resonance angiography magnetic resonance vascular studies cerebral blood vessels

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